Use of parapox B2L protein to modify immune responses to administered antigens

ABSTRACT

The Parapox B2L virus envelope protein is used as an adjuvant to enhance a subject&#39;s response to an administered antigen. Both antibody and cellular immune responses can be modified. B2L protein is particularly useful as an adjuvant for poorly immunogenic tumor vaccines and subunit vaccines, such as those useful for preventing and/or treating flu, tuberculosis, respiratory syncytial virus, anthrax and HIV.

This application is a continuation under 35USC120 of PCT application No.PCT/US02/38971, filed Dec. 6, 2002, published as WO 03050135 on Jun. 19,2003, which claims the benefit of provisional application Serial No.60/336,694 filed Dec. 7, 2001.

This invention was funded in part by DARPA Grant No N652369915426,Account number 36001, by which the US Government may have certain rightsin this invention.

FIELD OF THE INVENTION

The invention relates to the use of a B2L viral envelope protein of aParapox virus as a vaccine adjuvant.

BACKGROUND OF THE INVENTION

Cutaneous Parapox virus ovis causes recruitment of epidermal dendriticcells to the infection site in sheep and subsequent cell-mediatedimmunity (Lear et al., Eur. J. Dermatol. 6, 135-40, 1996; Haig et al.,Comp Immun. Microbiol. Infect. Dis. 20 197-204, 1997). AttenuatedParapox viruses can be used to induce Paradox-specific immunity. U.S.Pat. No. 6,162,600. In addition, the highly attenuated strain D1701(Baypamun HK®) is used as a non-specific immunomodulator (Buttner etal., Immunol. Microbiol. Infect. Dis. 16, 1-10, 1993) to promoteimmunity to heterologous pathogens.

Attenuation of Parapox virus, however, is time-consuming, taking from100 to 200 culture passages; according to WO 95/22978, it takes fromthree to five years to perform each 100 passages, depending on thespecies of virus used. Attenuation can, therefore, “encompass a periodlasting from ten to twenty years.” See WO 95/22978, page 9.

WO 95/22978 discloses the use of combinations of two or more individualParapox virus components as “multipotent paramunity inducers” for use asadjuvant therapy for tumors and the prevention of metastases. Thecomponents can be individual polypeptides or detached envelopes ofpoxviruses. WO 95/22978, however, does not disclose any particular viralpolypeptides other than the viral fusion protein and adsorption protein.Moreover, WO 95/22978 teaches that the disclosed paramunity inducershave virtually no immunogenic properties.

There is a need in the art for simple, effective vaccine adjuvants thatcan be used to enhance immune responses against tumors and dysplasticlesions and against exogenous pathogens.

SUMMARY OF THE INVENTION

It is an object of the invention to provide reagents and methods formodifying immune responses to administered antigens. This and otherobjects of the invention are provided by one or more of the embodimentsdescribed below.

One embodiment of the invention provides a method of enhancing an immuneresponse to a vaccine composition. The method involves administering toa subject in need thereof (a) an effective amount of a B2L viralenvelope protein of a Parapox virus and (b) a vaccine compositioncomprising an active component. The adjuvant B2L viral envelope proteinthereby enhances the immune response to the vaccine composition.

Another embodiment of the invention provides a pharmaceuticalcomposition comprising a B2L viral envelope protein of a Parapox virusand a vaccine composition comprising an active component.

Yet another embodiment of the invention provides a pharmaceuticalcomposition comprising a nucleic acid molecule encoding a B2L viralenvelope protein of a Parapox virus and a vaccine composition comprisingan active component.

Thus, the invention provides pharmaceutical compositions and methodsusing B2L protein to modify immune responses to administered antigens.

DETAILED DESCRIPTION OF THE INVENTION

The invention is based on the ability of a Parapox viral envelopeprotein termed “B2L” to act as an adjuvant, i.e., to augment orotherwise modify a subject's immune response to an administered antigenand/or an active component of a vaccine. Administered antigens include,but are not limited to, cells expressing tumor antigens, attentuated orkilled pathogens and antigenic components thereof or nucleic acidsencoding the antigenic components.

Both antibody and cellular immune responses can be modified. B2L proteinis particularly useful as an adjuvant for poorly immunogenic tumorantigens and subunit vaccines, such as those useful for preventingand/or treating flu, tuberculosis, respiratory syncytial virus, anthraxand HIV.

B2L is the second open reading frame in the BamH1 B fragment of the Orfvirus genome (Sullivan et al., Virology 202, 968-73, 1994). Prior workteaches that, as the activity of epitopes responsible forantigen-specific immunization decrease, adjuvant activity of thepreparations increases. See WO 95/22978, page 4. B2L is an immunogenicprotein; in fact, B2L protein is one of a few Orf virus proteins towhich a strong antibody response can be mounted in sheep. Sullivan etal., 1994. Thus, it is surprising that purified B2L protein itself hasadjuvant activity.

B2L proteins for use in the compositions and methods described hereinare those of the Parapoxvirus genus, such as Orf virus (OV),particularly the Parapox ovis strains NZ2, NZ7, NZ10, and D1701. Orfviruses are reviewed in Robinson & Balassu, Vet. Bull 51, 771, 1981;Robinson & Lyttle, in Binns & Smith, eds., recombinant poxviruses,Chapter 9, pp. 306-17, CRC Press, Boca Raton, 1992. An amino acidsequence for the B2L protein of OV NZ2 is disclosed in Sullivan et al.,Identification and characterization of an orf virus homologue of thevaccinia virus gene encoding the major envelope antigen p37K, Virology202 (2), 968-73, 1994, and is shown in SEQ ID NO:2. A coding sequencefor SEQ ID NO:2 is shown in SEQ ID NO:1. The amino acid sequences of theB2L proteins obtained from D1701 and NZ2 are highly conserved. The aminoacid sequence of the D1701 protein is shown in SEQ ID NO:4. A codingsequence for SEQ ID NO:4is shown in SEQ ID NO:3.

Purified B2L protein is separated from other compounds that normallyassociate with the B2L protein in the virus, such as other envelopecomponents. A preparation of purified B2L protein is at least 80% pure;preferably, the preparations are 90%, 95%, or 99% pure. Purity of thepreparations can be assessed by any means known in the art, such asSDS-polyacrylamide gel electrophoresis.

Purified B2L protein for use in compositions and methods of theinvention can be purified from Parapox viruses or from cells infected bythe viruses, by recombinant DNA methods, and by chemical synthesis.Purification methods include, but are not limited to, size exclusionchromatography, ammonium sulfate fractionation, ion exchangechromatography, affinity chromatography, and preparative gelelectrophoresis.

B2L protein can be expressed recombinantly, after insertion of B2Lcoding sequences into an expression vector that contains the necessaryelements for the transcription and translation of the inserted codingsequence. Maintenance of orf viruses in culture is disclosed in WO97/37031. A preferred system for maintaining and expressing B2L proteinis HKB11 cells transfected with B2L in a vector such as a p2ToP, pCEP4,or pcDNA3.1 vector (Invitrogen). Recombinantly produced B2L protein canbe secreted into the culture medium and purified. Methods for producingproteins recombinantly are well known to those skilled in the art.

A B2L protein also can be produced using chemical methods to synthesizeits amino acid sequence, such as by direct peptide synthesis usingsolid-phase techniques (Merrifield, J. Am. Chem. Soc. 85, 2149-2154,1963; Roberge et al., Science 269, 202-204, 1995). Protein synthesis canbe performed using manual techniques or by automation. Optionally,fragments of a B2L protein can be separately synthesized and combinedusing chemical methods to produce a full-length molecule.

“B2L protein” as used herein includes both functional portions of B2Land full-length or partial biologically active B2L variants.Biologically active variants (i.e., variants that possess adjuvantactivity) comprise amino acid substitutions, insertions, and/ordeletions with respect to the amino acid sequences shown in SEQ ID NOS:2or 4. Amino acid substitutions are defined as one for one amino acidreplacements. They are conservative in nature when the substituted aminoacid has similar structural and/or chemical properties. Examples ofconservative replacements are substitution of a leucine with anisoleucine or valine, an aspartate with a glutamate, or a threonine witha serine. Biologically active variants can comprise 1, 2, 3, 4, 5, 6, 7,8, 9, 10, 12, 15, 18, 20, 25, or 30 or more conservative amino acidsubstitutions as long as adjuvant activity of the B2L variant ismaintained.

Amino acid insertions or deletions are changes to or within an aminoacid sequence. They typically fall in the range of about 1 to 5 aminoacids (i.e., 1, 2, 3, 4, or 5). Guidance in determining which amino acidresidues can be substituted, inserted, or deleted without abolishingbiological or immunological activity of a B2L protein can be found usingcomputer programs well known in the art, such as DNASTAR software.Biological activity of a B2L protein having an amino acid substitution,insertion, and/or deletion can be tested, for example, as described inExample 1.

Functional portions of B2L comprising, for example, 25, 50, 75, 100,125, 150, 175, 200, 225, 250, 275, 300, 325, 350, 360, 370, 375, or 377amino acids, also can be used in the compositions and methods of theinvention, provided that the portions of B2L retain biological activity,e.g., the ability to enhance an immune response and/or exert achemotactic effect on enriched dendritic cell populations.

Purified B2L protein can be used in pharmaceutical compositions.Pharmaceutical compositions of the invention can be used to boost immuneresponses in mammals, including laboratory animals (e.g., mice, rats,hamsters, guinea pigs), companion animals (e.g., dogs, cats), farmanimals (e.g., horses, cows, sheep, pigs, goats), and humans.

Pharmaceutical compositions of the invention include a pharmaceuticallyacceptable carrier. Typically these will be sterile formulations in adiluent or vehicle that is free of pyrogenic components. Buffers,stabilizers, and the like can be included, as is known in the art.Optionally, pharmaceutical compositions include conventional adjuvants,such as aluminum hydroxide and aluminum phosphate (collectively commonlyreferred to as alum), saponins complexed to membrane protein antigens(immune stimulating complexes), pluronic polymers with mineral oil,killed mycobacteria in mineral oil, Freund's complete adjuvant,bacterial products, such as muramyl dipeptide, and lipopolysaccharides.

If desired, B2L protein can be coupled to an antigen. Means of makingsuch molecules are well known in the art. For example, coupled moleculescan be synthesized chemically or produced by covalently linking twopolypeptide segments or by standard procedures in the art of molecularbiology. Recombinant DNA methods can be used to prepare fusion proteins,for example, by making a DNA construct which comprises B2L codingsequences in proper reading frame with nucleotides encoding apolypeptide to be coupled with B2L and expressing the DNA construct in ahost cell, as is known in the art. Many kits for constructing fusionproteins are available from companies such as Promega Corporation(Madison, Wis.), Stratagene (La Jolla, Calif.), CLONTECH (Mountain View,Calif.), Santa Cruz Biotechnology (Santa Cruz, Calif.), MBLInternational Corporation (MIC; Watertown, Mass.), and QuantumBiotechnologies (Montreal, Canada; 1-888-DNA-KITS).

B2L-containing compositions are co-administered with a particularantigen or vaccine composition. “Co-administration” includesadministration of B2L and the antigen or vaccine composition separatelyor in the same composition.

Vaccine compositions comprise one or more active components, e.g., atumor antigen or an attenuated or killed pathogen or an antigeniccomponent thereof. Antigenic components include any component that isrecognized by cells of the immune system. Suitable tumor antigensinclude, but are not limited to, α-fetoprotein, BAGE, β-HCG, CEA, ESO,GAGE, gangliosides, Her-2/neu, HPV E6/E7, immunoglobulins, MAGE-1,MAGE-2, MAGE-3, MAGE-4, MAGE-12, MART-1, Melan-A, melanoma antigen gp75,gp100, MN/G250, MUC1, MUC2, MUC3, MUC4, MUC18, PSA, PSM, RAGE, ras,SART-1, telomerase, thyroperoxidases, tyrosinases, and p53.

Vaccine compositions also can include a pathogen. The pathogen can be,e.g., an attenuated or killed virus, bacterium, mycoplasm, parasite,yeast, fungus, prion, or a protozoan. Suitable pathogens include humanimmunodeficiency viruses, Herpes viruses, hepatitis viruses, poxviruses, flu viruses, measles, mumps, rubella, rabies, respiratorysyncytial viruses, Bacillus anthracis, Bordetella pertussis, Borreliaburgdorferi, Clostridium tetani, Corynebacterium diphtheriae,Haemophilus influenza B, Neisseria meningitidis, Salmonella typhi,Streptococcus pneumoniae, and Vibrio cholerae. The active component alsocan be, for example, an immunogenic fragment, extract, subunit,metabolite, or recombinant construct of such a pathogen. Optionally, theactive component can be mixed with a pharmaceutically acceptable carrierand/or a conventional adjuvant, as described above.

Adjuvant compositions comprising B2L protein can be administeredsequentially or simultaneously with a vaccine composition, including apoorly immunogenic subunit vaccine. If desired, the B2L protein can bepresent in the vaccine composition. Suitable routes of administrationinclude, without limitation, subcutaneous, intravenous, nasal,ophthalmic, transdermal, intramuscular, intradermal, intragastric,perlingual, alveolar, gingival, intraperitoneal, intravaginal,pulmonary, rectal, and oral administration. Administration can be by anysuitable means, including injection, topical administration, ingestion,or inhalation. Single and/or multiple administrations are contemplated.

Optionally, B2L protein can be administered using a nucleic acidmolecule encoding the protein. The nucleic acid molecule can be eitherDNA, RNA, or a DNA/RNA chimera. Use of DNA-encoded elicitors of immuneresponses is discussed, for example, in McDonnel & Askari, New Engl J.Med. 334, 42-45, 1996; Robinson, Can. Med. Assoc. J. 152, 1629-32, 1995;Fynan et al., Int. J. Immunopharmacol. 17, 79-83, 1995; Pardoll &Beckerleg, Immunity 3, 165-69, 1995, and Spooner et al., Gene Therapy 2,173-80, 1995. Chimeric RNA/DNA oligonucleotide based gene therapy isdiscussed in Lai & Lien, Expert Opin Biol Ther 2001 January; 1(1):41-7.

A variety of delivery systems, both viral and non-viral, can be used toadminister the B2L-encoding nucleic acid molecule. Such delivery systemsinclude, but are not limited to, naked plasmid DNA, viral expressionvectors, and nucleic acid molecules in conjunction with a liposome or acondensing agent. See U.S. Pat. No. 6,303,372.

The determination of a therapeutically effective dose of B2L is wellwithin the capability of those skilled in the art. A therapeuticallyeffective dose refers to that amount of active ingredient (i.e., B2Lprotein or nucleic acid encoding B2L) that results in an augmentation ofthe immune response to a co-administered antigen, compared to that whichoccurs in the absence of the therapeutically effective dose.

The therapeutically effective dose can be estimated initially either incell culture assays or in animal models, usually mice, rats, rabbits,dogs, or pigs. The animal model also can be used to determine theappropriate concentration range and route of administration. Suchinformation can then be used to determine useful doses and routes foradministration in humans.

Therapeutic efficacy and toxicity, e.g., ED50 (the dose therapeuticallyeffective in 50% of the population) and LD50 (the dose lethal to 50% ofthe population), can be determined by standard pharmaceutical proceduresin cell cultures or experimental animals. The dose ratio of toxic totherapeutic effects is the therapeutic index, and it can be expressed asthe ratio, LD50/ED50.

Pharmaceutical compositions that exhibit large therapeutic indices arepreferred. The data obtained from cell culture assays and animal studiesare used in formulating a range of dosage for human use. The dosagecontained in such compositions is preferably within a range ofcirculating concentrations that include the ED50 with little or notoxicity. The dosage varies within this range depending upon the dosageform employed, sensitivity of the patient, and the route ofadministration.

Suitable dosages and treatment regimens for administration of either B2Lprotein or nucleic acid molecules encoding B2L include, but are notlimited to, daily, twice-or three-times weekly, weekly, bi-weekly,monthly, bimonthly, or yearly treatments of about 1,5,10,15, 20, 25, 50,75,100, or 200 ug/m² (or approximately 0.05, 0.1, 0.2, 0.25, 0.3, 0.5,0.75,1, 2, 5, or 10 mg/kg). Preferred routes of administration includesubcutaneous, intradermal, intramuscular administration. The exactdosage, treatment regimen, and route of administration, however, will bedetermined by the practitioner, in light of factors related to thesubject that requires treatment.

All patents, patent applications, and references cited in thisdisclosure are expressly incorporated herein by reference in theirentireties. The above disclosure generally describes the presentinvention. A more complete understanding can be obtained by reference tothe following specific example, which is provided for purposes ofillustration only and is not intended to limit the scope of theinvention.

EXAMPLES

B2L provides adjuvant activity when coadministered with a tumor antigen.Tumor peptides frequently are weak immunogens, and immune responses tothem typically require that they be administered together with anadjuvant. A tumor vaccine consisting of an emulsion prepared withMontanide ISA 51 containing 100 ug of a melanoma peptide (TRP-2) and 100ug of either V5His6-tagged B2L or and irrelevant protein (hSLC; humansecondary lymphoid chemokine) was administered subcutaneously at thebase of the tail three days after implantation of a melanoma tumor knownto express the antigen included in the vaccine. Tumor growth wasmonitored until the nodules reached the volume permitted by an approvedanimal care and use protocol. By comparison with animals given the tumorantigen together with an irrelevant protein, there was a trend towardreduced tumor growth in mice treated with tumor antigen together withtagged B2L. The results are consistent with B2L's augmentation of animmune response to the TRP-2 tumor antigen, which slowed the growth ofthe tumor expressing this antigen.

4 1 1137 DNA PARAPOX 1 atgtggccgt tctcctccat ccccctgggc gccgactgccgcgtcgtgga gacgctgccc 60 gcagaggtgg cgtctttggc gcagggcaac atgagcaccctcgactgctt caccgctatc 120 gccgagtccg cgaagaagtt cttgtacatc tgcagcttctgctgcaacct gagctccacc 180 aaggagggcg tcgacgtcaa ggacaagctc tgcacgctcgccaaggaggg cgtagacgtc 240 acgctgctcg tggacgtgca gagcaaggac aaggacgcggacgagctgcg cgaggcgggc 300 gtcaactact acaaggtcaa ggtgtccacc aaggagggcgtcggcaacct tctcggcagc 360 ttctggctct cggacgccgg gcactggtac gtgggaagcgcctcgctcac gggcgggtcc 420 gtgtccacca tcaagaacct cgggctctac tccaccaacaagcacctggc ctgggacctc 480 atgaaccgct acaacacctt ctactccatg atcgtggagccgaaggtgcc gttcacgcgg 540 ctctgctgcg ccatcgtcac gcccacggcc acgaacttccacctcgacca ctccgggggc 600 ggcgtattct tctcggactc gccggagcgc ttcctaggcttctaccgcac gctcgacgag 660 gacctcgtgc tgcaccgcat cgagaacgcc aagaacagcatcgacctctc gctgctctcg 720 atggtgccgg tgatcaagca cgccagcgcc gtggagtactggccgcagat cattgacgcg 780 ctgctgcgcg cggccatcaa ccgcggcgtg cgcgtgcgcgtgatcattac cgagtggaag 840 aacgcggacc cgctttcggt ctcggccgcg cgcagcctcgacgactttgg cgtcggcagc 900 gtggacatgt ccgtgcgcaa gttcgtggta cccggccgggacgacgccgc gaacaacact 960 aagctgctca tcgtggacga caccttcgcg cacctcacggtcgccaacct cgacggcacg 1020 cactaccgct accacgcctt cgtgagcgtg aacgccgagaagggcgacat cgtcaaggac 1080 ctgtccgcgg tcttcgagcg ggactggcgc tcggagttctgcaagccaat aaattaa 1137 2 378 PRT PARAPOX 2 Met Trp Pro Phe Ser Ser IlePro Leu Gly Ala Asp Cys Arg Val Val 1 5 10 15 Glu Thr Leu Pro Ala GluVal Ala Ser Leu Ala Gln Gly Asn Met Ser 20 25 30 Thr Leu Asp Cys Phe ThrAla Ile Ala Glu Ser Ala Lys Lys Phe Leu 35 40 45 Tyr Ile Cys Ser Phe CysCys Asn Leu Ser Ser Thr Lys Glu Gly Val 50 55 60 Asp Val Lys Asp Lys LeuCys Thr Leu Ala Lys Glu Gly Val Asp Val 65 70 75 80 Thr Leu Leu Val AspVal Gln Ser Lys Asp Lys Asp Ala Asp Glu Leu 85 90 95 Arg Glu Ala Gly ValAsn Tyr Tyr Lys Val Lys Val Ser Thr Lys Glu 100 105 110 Gly Val Gly AsnLeu Leu Gly Ser Phe Trp Leu Ser Asp Ala Gly His 115 120 125 Trp Tyr ValGly Ser Ala Ser Leu Thr Gly Gly Ser Val Ser Thr Ile 130 135 140 Lys AsnLeu Gly Leu Tyr Ser Thr Asn Lys His Leu Ala Trp Asp Leu 145 150 155 160Met Asn Arg Tyr Asn Thr Phe Tyr Ser Met Ile Val Glu Pro Lys Val 165 170175 Pro Phe Thr Arg Leu Cys Cys Ala Ile Val Thr Pro Thr Ala Thr Asn 180185 190 Phe His Leu Asp His Ser Gly Gly Gly Val Phe Phe Ser Asp Ser Pro195 200 205 Glu Arg Phe Leu Gly Phe Tyr Arg Thr Leu Asp Glu Asp Leu ValLeu 210 215 220 His Arg Ile Glu Asn Ala Lys Asn Ser Ile Asp Leu Ser LeuLeu Ser 225 230 235 240 Met Val Pro Val Ile Lys His Ala Ser Ala Val GluTyr Trp Pro Gln 245 250 255 Ile Ile Asp Ala Leu Leu Arg Ala Ala Ile AsnArg Gly Val Arg Val 260 265 270 Arg Val Ile Ile Thr Glu Trp Lys Asn AlaAsp Pro Leu Ser Val Ser 275 280 285 Ala Ala Arg Ser Leu Asp Asp Phe GlyVal Gly Ser Val Asp Met Ser 290 295 300 Val Arg Lys Phe Val Val Pro GlyArg Asp Asp Ala Ala Asn Asn Thr 305 310 315 320 Lys Leu Leu Ile Val AspAsp Thr Phe Ala His Leu Thr Val Ala Asn 325 330 335 Leu Asp Gly Thr HisTyr Arg Tyr His Ala Phe Val Ser Val Asn Ala 340 345 350 Glu Lys Gly AspIle Val Lys Asp Leu Ser Ala Val Phe Glu Arg Asp 355 360 365 Trp Arg SerGlu Phe Cys Lys Pro Ile Asn 370 375 3 1137 DNA PARAPOX 3 atgtggccgttctcctccat ccccgtgggc gcccaatgcc gcgtcttgga aacgctgccc 60 gcagaggtggcgtccctggc gcagggcaac atgagcaccc tcgactgctt caccgccatc 120 gccgagtccgcgaagaaatt tttgtacatc tgcagcttct gctgcaacct gagctccacc 180 aaggagggcgtcgacgtcaa agacaagctc tgcacgctcg ccaaggaagg cgttgacgtc 240 acgctgctcgtggacgtgca gagcaaggac aaggacgcgg acgaactgcg cgcggcgggc 300 gtcaactactacaaggtcaa agtgtccacg cgggaaggcg tcggcaacct tctcggcagc 360 ttctggctctcggacgccgg gcactggtac gtgggcagcg cctcgctcac gggcgggtcc 420 gtgtccaccatcaagaacct cgggctctac tccaccaaca agcacctggc ctgggacctc 480 atgaaccgctacaacacctt ctactccatg atcgtggagc cgaaggtgcc gttcacgcgg 540 ctctgctgcgccgtcgtcac gcccacggcc acgaacttcc acctcaacca ctccgggggc 600 ggcgtattcttctcggactc gccggagcgc ttcctaggct tctaccgcac gctcgacgag 660 gacctcgtgctgcaccgcat cgagaacgcc aagaacagca tcgacctctc gctgctctcg 720 atggtgccggtgatcaagca cgccggcgcc gtggagtact ggccgcggat catagacgcg 780 ctgctgcgcgcggccatcaa ccgcggcgtg cgcgtgcgcg tgatcatcac cgagtggaag 840 aacgcggacccgctgtcggt ctcggccgcg cgcagcctcg acgactttgg cgtcggtagc 900 gtggacatgtccgtgcgcaa gttcgtggta cccggccggg acgacgctgc gaacaacacc 960 aagctgcttatcgtggacga caccttcgcg cacctcacgg tcgccaacct cgacggcacg 1020 cactaccgctaccacgcctt cgtgagcgtg aacgccgaga agggcgacat cgtcaaggac 1080 ctgtccgcggtcttcgagcg ggactggcgc tcggagtttt gcaagccaat aaattaa 1137 4 378 PRTPARAPOX 4 Met Trp Pro Phe Ser Ser Ile Pro Leu Gly Ala Gln Cys Arg ValLeu 1 5 10 15 Glu Thr Leu Pro Ala Glu Val Ala Ser Leu Ala Gln Gly AsnMet Ser 20 25 30 Thr Leu Asp Cys Phe Thr Ala Ile Ala Glu Ser Ala Lys LysPhe Leu 35 40 45 Tyr Ile Cys Ser Phe Cys Cys Asn Leu Ser Ser Thr Lys GluGly Val 50 55 60 Asp Val Lys Asp Lys Leu Cys Thr Leu Ala Lys Glu Gly ValAsp Val 65 70 75 80 Thr Leu Leu Val Asp Val Gln Ser Lys Asp Lys Asp AlaAsp Glu Leu 85 90 95 Arg Ala Ala Gly Val Asn Tyr Tyr Lys Val Lys Val SerThr Arg Glu 100 105 110 Gly Val Gly Asn Leu Leu Gly Ser Phe Trp Leu SerAsp Ala Gly His 115 120 125 Trp Tyr Val Gly Ser Ala Ser Leu Thr Gly GlySer Val Ser Thr Ile 130 135 140 Lys Asn Leu Gly Leu Tyr Ser Thr Asn LysHis Leu Ala Trp Asp Leu 145 150 155 160 Met Asn Arg Tyr Asn Thr Phe TyrSer Met Ile Val Glu Pro Lys Val 165 170 175 Pro Phe Thr Arg Leu Cys CysAla Val Val Thr Pro Thr Ala Thr Asn 180 185 190 Phe His Leu Asn His SerGly Gly Gly Val Phe Phe Ser Asp Ser Pro 195 200 205 Glu Arg Phe Leu GlyPhe Tyr Arg Thr Leu Asp Glu Asp Leu Val Leu 210 215 220 His Arg Ile GluAsn Ala Lys Asn Ser Ile Asp Leu Ser Leu Leu Ser 225 230 235 240 Met ValPro Val Ile Lys His Ala Gly Ala Val Glu Tyr Trp Pro Arg 245 250 255 IleIle Asp Ala Leu Leu Arg Ala Ala Ile Asn Arg Gly Val Arg Val 260 265 270Arg Val Ile Ile Thr Glu Trp Lys Asn Ala Asp Pro Leu Ser Val Ser 275 280285 Ala Ala Arg Ser Leu Asp Asp Phe Gly Val Gly Ser Val Asp Met Ser 290295 300 Val Arg Lys Phe Val Val Pro Gly Arg Asp Asp Ala Ala Asn Asn Thr305 310 315 320 Lys Leu Leu Ile Val Asp Asp Thr Phe Ala His Leu Thr ValAla Asn 325 330 335 Leu Asp Gly Thr His Tyr Arg Tyr His Ala Phe Val SerVal Asn Ala 340 345 350 Glu Lys Gly Asp Ile Val Lys Asp Leu Ser Ala ValPhe Glu Arg Asp 355 360 365 Trp Arg Ser Glu Phe Cys Lys Pro Ile Asn 370375

What is claimed is:
 1. A method of enhancing an immune response to anantigen, comprising the steps of: administering to a subject mammal inneed thereof (a) an effective amount of a B2L viral envelope protein ofa Parapox virus, wherein the B2L protein is unassociated with otherenvelope components naturally associated with the B2L protein in thevirus, and (b) an antigen, whereby the B2L protein acts as an adjuvantto enhance the immune response to the antigen; and detecting a resultantenhanced, specific immune response to the antigen.
 2. The method ofclaim 1 wherein the B2L protein and the antigen are administeredsequentially.
 3. The method of claim 1 wherein the B2L protein and theantigen are administered simultaneously.
 4. The method of claim 1wherein the B2L protein and the antigen are administered simultaneouslyas a fusion protein comprising the B2L protein and the antigen.
 5. Themethod of claim 1 wherein the B2L protein is administered by means of anucleic acid encoding the B2L protein.
 6. The method of claim 1 whereinthe antigen is administered by means of a nucleic acid encoding theantigen.
 7. The method of claim 1 wherein the antigen is administered asan attenuated or killed pathogen comprising the antigen.
 8. The methodof claim 1 wherein the antigen is a tumor antigen.
 9. The method ofclaim 1 wherein the B2L protein and the antigen are administered byinjection.
 10. The method of claim 1 wherein the B2L protein and theantigen are administered intradermally.
 11. The method of claim 1wherein the Parapox virus is a Parapox virus ovis strain selected fromthe group consisting of NZ2, NZ7, NZ10, and D1701.
 12. The method ofclaim 1 wherein the mammal is a human.
 13. A pharmaceutical compositionfor enhancing an immune response to an antigen, the compositioncomprising: a B2L viral envelope protein of a Parapox virus, or anucleic acid encoding said B2L protein, wherein the B2L protein isunassociated with other envelope components naturally associated withthe B2L protein in the virus; and an antigen or a nucleic acid encodingsaid antigen, wherein administered to a subject mammal in need thereof,the B2L protein of the pharmaceutical composition acts as an adjuvant toenhance a specific immune response to the antigen.